Telephone-circuit.



,643. PATENTED PBB.18`, i908 C. M. JACOBS @L W. J. THoRRoWGoou TELEPHONECIRCUIT.

APPLIGATXON FILED 0011.12.1906.

l has phone receiver does not respond to currents `pore winding of thparallel, the object .regarded from the point of view of telephoneinvention.

' CHARLES-MARKS JAcoBs. or

READING, AND WILLIAM JonN v'rnonnoweoon or WIMBLEDON PARK, ENGLAND,

- TELEPHONE-CIRCUIT.

To all whom it may concern: I Be it known that we, CHARLES MARK JA-cons, electrical engineer, and WILLIAM -JOHN Tnonnoweoon, telegraphengineer,'both subjects of the King of Great Britain, resid- Ing,respective] ,at St. Cuthberts, Alexan- .a Road, Rea in in the county ofBerks, England, and 2 Waldemar road, Wimbledon Park, in the county ofSurrey, England, have invented certain new and. useful Improvements inTelephone-Circuits, of which thefollowing is a specification, (for whichwe have applied for a patent in Great Britain, dated the 13th January,1906, No. 997.)

In a known constructionv a telephone receiver is wound with aphonopore'coil, which serves as a condenser of very small capacity, sothat whenv the receiver is used on an unbalanced circuit, the disturbingeffect of currents of low frequencies is not perceived in the tele hone.Inusing this tele henereceiverit heen connectedwithits p onopore coil inseries with the secondary of the telephone transformer, an arrangementwhich is disadvantageous in that the resistance of the phonopore coilsvenfeebles the currents induced in the secondary.

By the resent invention the secondary of the telephone transformer `andthe phonoe receiver are arranged in being to reduce considerably or toeliminate the effect in the telephone receiver ofcurrents of low freuencies and to insure that the volume of t e telephone currents throughthe telephone relceiver shall be a maximum. l

The fact that a phonoporically wound teleof lower than telephoniefrequency is probably de tothe fact that such a telephone receiver actspractically as a condenser of small capacity, and on this account itbecomes necessary 1n orderto obtain a maximum effect SpecificationefLetters Patent. 'Appiicaion nea amber 12.1906. 'sentira 338.679.

vthe latter.-

in the receiver with` telephonie currents that the terminals of thetelephone receiver shall he connected with such points of the circuit ashave a maximum di erence of potential currents. n v The accompanyingdiagrams illustrate the Figure 1 shows the arrangement of a two wireused for telegraphic purposes. Figs. 2

Patented Feb. 18, 1908.

and 3 show alternative arrangements of an intermediate tele hone. Fig.Sashows the arrangement of Fig.. 1 applied to an intermediate station.

In each of these arrangements a is the hat'- tery, Z2 the transmitter, cthe primary of the telephone transformer and the secondary of thistransformer connected in the line Z. Referring to Fig. l thephonoporically wound receiversof the tele hones at stations A and A areconnected in eak to earth E at the points i', and of the line Z. Owingto the self-induction ofthe secondaries d the potential of the telephonecurrents impressed upon the circuit by means of the primaries c andsecondaries d has an appreciable drop through The phonoporic receivers gbei connected in leak to earth at the points t' an y' aretherefore-connected'to points of maximum potential so far as concernstelephone currents impressed by means of the primaries c and secondariesThe impedance offered to telephone currents by the secondaries Z being areciable, -while the receivers g offer practica y no impedance totelephone currents, more kof the telephone currents impressed on -thecircuit at A or A will pass through the receivers g than through thesecondary at A or A. The condensers f, which have considerable capacity,are connected in leak to earth at the terminals Zt and Zc of the.secondaries Z so that if the line Z has considerable ohmic resistanceor impedance to the leftof Za, or the right of Zr, telephone currentscan get to earth at the points Zi and Zc and not suffer attenuationthrough having to traverse the y.Whole length of the telegrzphic line Z.

n the case of an intermediate telephone the receiver maybe in leak onthe side of the secondaryfof the telephone which is nearer to thestationI with which the user 1s speaking, J

for convenience,` therefore, there may be a receiver on each side 'ofthe secondary or the receiver may be provided with a switch forconnecting it with either side as shown in Fig. 3a. Fig. 2 shows anarrangement Whereby one receiver only is sufficient at an intermediatestationwithout a switch being necessary. In this case the terminals ofthe receiver g are connected in shunt across the lterminals of thesecondary al. The impeance to telephone currents being greater throughthe secondaryd than through the reduction coil is not included directlyin the line circuit but is connected in leak from line to earth througha condenser, the latter being necessary in order to prevent telegraphiccurrents from the instruments such as m, n, in Fig. 1 passing directlyrto earth at this point. The phonoporic telephone receiver is alsoconnected [in leak from line to earth, the two arrangements consequentlybeing in shunt with each other. Although the secondary d and condenser fare in shunt with the phonoporic telephone receiver g, they do notmaterially affect thev volume of the received telephone currents onaccount of the self induction of the secondary.

Having thus described the nature of this invention and the best means Weknow of carrying the same into practical eiiect We claim: f I 1. In asystem for eliminating or reducing the infiuence of disturbing currentson telephone circuits7 the combination of a telephone transformer and aphonoporically Wound receiver, thevlatter being connected across theterminals of the secondary Winding of the.

more of the telephone currents im.

transformer, the 4said secondary Winding being -directly in the line.

2. In a system for eliminating or reducing the influence of disturbingcurrents on telephone circuits, the combination of a telephonetransformer, aphono orically Wound receiver and ya condenser, t e saidreceiver and condenser being connected in series with each other acrossthe terminals of the secondary Winding of the transformer and havingtheir intermediate point connected with earth.

3. In a system for eliminating or reducing the influence of disturbingcurrents on telephone circuits, the combination of a telephonetransformer, a phono orically Wound receiver and a condenser, t 'e saidreceiver and condenser being connected in series with arywinding of thetransformer and having their `intermediate point connected with earth,and the said secondary Winding being .connected directly-in the line.

In testimony whereof We have signed our names to this speclfication inthe presence of two subscribing Witnesses.

' CHARLESv MARK JACOBS.

WILLIAM JQHN THORRWGOOD.

Witnesses:

JOSEPH MILLARD, WALTER J; SKERTEN.

each other across the terminals of the second-

